Classifier



Jim. 11, 1938. HAULTAIN 2,104,926

CLASSIFIER Filed April 4, 1935 2 Sheets-Sheet l jTwemTor ]-[.E. T. H awn Wain Jan. 11, 1938. H. E. T. HAULTAIN 2,104,926

' CLAS'SIFIER Filed April 4, 19:55 2 Sheets-Sheet 2 Fatented Jan. ll, l3$

pariah stares OLASSH'IER Herbert E. T. Haultain, Toronto, Gntario, Canada Application April 4, 1935, Serial No. 14,577

16 Claims.

This invention relates to classifiers for separating the coarse from the fine particles of crushed rock suspended in water and particularly to that type of classifier which is provided with a settling-chamber and an incline up which the material that settles is conveyed by mechanical means and is returned to a grinding unit for lretreatment thereby, and is subsequently 'returned to the settling chamber of the classifier, the latter and the grinding unit being in a closed circuit. 7 The main separation is efiected in the settling chamber and on account of the unstable density conditions of the pulp within the chamber there are set up cycles of changes of density or surges which are objectionable in that they affect the uniformity of the separation, under some conditions more seriously than others, and with the classifiers now in use the skill of the operator is taxed in trying to keep the surges to a suitable minimum.

The manufacturers of classifiers have tried to overcome these surges by increasing the size of the settling chambers and the quantity of material in the circuit. While this tends to absorb the surges, the cost of the apparatus and the time required to check any changes made by the operator are also increased. The object of the present invention is to devise simple and inexpensive apparatus which will produce a uniform separation by minimizing or eliminating the above mentioned objectionable feature, which may be applied in part to classifiers now in use, and which will facilitate a more accurate study of the eflect of any changes made in operating methods.

I attain my object by providing means for conveying a constant predetermined quantity of sands from the classifier to the grinding unit and for carrying the sands, which are carried up the incline by the mechanical conveyors, in excess of this predetermined quantity directly back to the settling chamber of the classifier.

The constructions are hereinafter more fully described and are illustrated in the accompanying drawings in which Fig. 1 is a diagrammatic view in side elevation of a classifier circuit showing myiapparatus applied thereto;

Fig. 2 a plan view of the classifier shown diagrammatically;

Fig. 3 a diagrammatic view of a modified form of my invention showing it built into a classifier;

and

Fig. 4 a diagrammatic of receptacle.

In the drawings like numerals of reference indicate corresponding parts in the difierent figures. I is a classifier of ordinary construction which includes an incline 2, a settling tank or chamber t, and a conveyor view of a modified form trolled by a gate Hl t which may be of the screw or rake type for carrying the settled product in the chamber up the incline 2 over the discharge end 5 thereof. The fine particles or slimes flow over a weir 6 and a feeder l is provided to direct the ore pulp into the chamber 3. This construction is well known and it has been the general practice to establish communication between the discharge 5 and the inlet 8 of a grinding mill 8 and between the outlet 8 of the mill 8 and the feeder 1 so that the classifier and the grinding mill are in a closed circuit. Of course the supply of material from the classifier to the mill is increased by a predetermined quantity of fresh material which may be directed into the inlet 8 by means. of a chute 9.

Instead of directing all the material or sands brought up the incline 2 from the chamber 3 to the grinding mill whether the quantity of sands be large or small, I convey only a predetermined quantity of such sands to the grinding mill. Any sands brought up the incline in excess of this predetermined quantity are returned directly to the settling chamber 3 without being passed through the grinding mill. This may be accomplished by any suitable means. In Figs. 1 and 2 is diagrammatically illustrated be readily used with existing classifiers. Beneath the discharge 5 of the classifier is positioned a receptacle l from the classifier. The bottom of the receptacle is provided with an outlet Ill beneath which a conveyor H, which may be of the endless belt type, is located. Preferably the receptacle is rectangular having an open bottom and the conveyor II is located adjacent the lower edges of the sides and one end of the receptacle to form a bottom therefor.

The depth of material on the conveyor is conwhich is adJustably carried at the lower edge of the other end of the receptacle. By varying the height of the gate relative to the conveyor II and by varying the speed of the latter, any predetermined quantityof sands may be fed from the receptacle to the grinding mill 8.

In operation the quantity of sands carried by the conveyor H in a given period of time will be slightly less than that received inv the same period of time-by the receptacle from the classifier discharge 5. A screw conveyor l2 may be employed to remove any surplus sands from the receptacle. The conveyor I2 is located across the upper portion of the receptacle with its axis substantially parallel to the discharge end of the classifier and discharges onto a conveyor IS. The latter directs the surplus sands into the settling chamber 3.

In the present classifiers, the conveyors 4 also serve as agitators in the chambers 3 and are driven at a constant rate of speed. As this speed for receiving all the sands of the pulp in the chamber 3, separate means are employed in my improved classifier for driving each of the conveyors li -and l2, [3 so that the speed of the conveyor H may be varied relative to that of the conveyors l2, l3 or to that of the conveyor 4. The above mentioned separate means for driving each of the conveyors H, I2 and I3 may include a pulley on each conveyor and a separate rheostat controlled electric motor for driving each pulley. The pulley |1on the conveyor I2 is connected by a belt l8 with the pulley on a motor I9 which is provided with a rheostat 20 for varying the speed of the motor. The pulley 2| on the conveyor II is driven by a belt 22 from a motor 23 provided with a rheostat 24. The pulley 25 on the conveyor l3 may also be driven from the motor IE or one similar thereto and controlled by the rheostat 20 so that the conveyors l2 and I3 will travel at substantially the same rate of speed. The drive for the conveyor 4 is well known in the art and is therefore not shown. The conveyor I2 is not used in .Fig. 3 and therefore the pulley 250. on conveyor |3b will be driven by motor l9.

Referring to Fig. 3, it will be noted that sepa-, rate agitators formed as for agitating the ore pulp in the settling chamber. These paddles are actuated back and forth in the chamber by any suitable means which may be varied in speed relative to the speed of the conveyor 4 which differs from the conveyor 4 in that it is not adapted to agitate the pulp in the chamber 3. Instead of using conveyors l2, l3 for returning the surplus sands from the receptacle I0, I show jets 12 for introducing upwardly directed streams of water intermediate the top and bottom of the receptacle which agitates the upper stratum of sands so that they may overflow into a launder l3. The latter may convey the overfiow directly to the chamher 3 'or to a conveyor l3 which discharges on to a launder l3 for directing the overflow to the chamber 3. Some of the fines or slimes in the excess material at the top of the receptacle which were withdrawn from the settling chamber with the sands will be separated therefromby the action of the water and carried into the launder l3 Thus the agitation not only causes the excess material to be returned directly to the settling chamber but separates the finer particles of ore from the coarser particles and facilitates the return of these finer particles to the chamber from which they may pass over the weir 6.

' Further, the separation of the sands and fines in the settling chamber 3 is facilitated by withdrawing the middlings therefrom. The fines at the top of the chamber fiow over the weir 6, the sands at the bottom of the chamber are withdrawn by the conveyor 4 or 4 Between the top layer of fines and the bottom layer of sands, an accumulatiom of what millmen term critical size material or middlings is being constantly built up. These middlings are about the size of the coarsest of the fines and have a tendency to remain intermediate the top and bottom of the chamber. A conduit 15 communicating with the chamber at a point intermediate its top and bottom is employed to'remove the middlings which may be directed to the grinding mill or to a separate classifier.

From this description it is obvious that the quantity of the material returned from the classlider to the grinding mill may be maintained paddles l4 are provided cluding the provisions for by-passing a portion of the sands discharged by the classifier to reclassify them in the settling chamber without passing them through the grinding unit. In other words, a direct circuit is established (between the receptacle ill and the chamber 3) within the closed circuit including the classifier and the grinding mill 8, whereby a predetermined quantity of material in the said closed circuit will be fed to the grinding mill by using the direct circuit for directly returning to the settling chamber any material in excess of the said predetermined quantity.

It will be understood that the receptacle l0 might be frusto-conical as shown in Fig. 4-. when certain types of coarse pulp are being separated. The gate I0 in this case, would be positioned to control the discharge from the outlet at the bottom of the receptacle and the conveyor ll would not be necessary.-

Pipes 16, I6 may be employed for supplying, water to the chute 9 and the launder H which forms part of the hereinbefore mentioned means for establishing communication between the outlet 8 of the grinding mill 8 and the feeder I of the settling chamber 3. The launder ll communicates with the inlet of a centrifugal pump having a pipe 1 connected with its outlet. Any suitable means may be employed to direct the material discharged from the pipe 1* to the feeder 1.

What I claim as my invention is:

1. In combination a classifier and a grinding mill in closed circuit, the classifier including a settling chamber having an overflow for the slimes or fine particles, the classifier also having a discharge end; means for drawing oif setclassifier; and means for returning any surplus discharged sands directly to the settling chamber of the classifier so that such surplus sands will vbe i e-classified before being re-ground.

2. In combination a classifier and a grinding mill in closed circuit, the classifier including a settling chamber and a discharge end for sands; means for drawing off settled sands from the settling chamber and discharging them over the said end; means for returning a quantity of the said discharged sands to the grinding mill so that they will be re-ground before rerentry to the chamber; means for varying the rate of return to the grinding mill; and means for returning any surplus discharged sands so withdrawn directly to the settling chamber of the classifier so that such surplus sands will be re-classified before being reground.

3. In combination a classifier and a grinding mill in closed circuit, the classifier including a settling chamber and a discharge end for sands; means for drawing off settled sandsfrom the settling chamber and discharging them over the said end; means for returning a quantity of the said discharged sends to the grinding mill so that they will be re-grcund before re-entry to the chamber; means for varying the rate of return to the grinding mill; means for returning sur plus discharged ,isands so withdrawn directly to the settling chamber of the classifier; and means for varying the rate of return to the settling chamber of any sands in excess of said predetermined quantity.

4. In combination a classifier and a grinding mill in closed circuit, the classifier including a settling chamber and a discharge end for sands; means for drawing ofi settled sands from the settling chamber and discharging them over the said end; means for returning a'predetermined quantity of the said discharged sands to the grinding mill so that they will be re-ground before re-entry to the chamber; means for returning any discharged surplus sands directly to the settling chamber oi the classifier; an agitator located in the settling chamber separate from the withdrawal means; and means for varying the relative rate of action of the withdrawal means and the agitator.

5. In combination with a classifier having a settling chamber provided with an overflow for the slimes or fine particles, the classifier also having a discharge end for sands, and a grinding unit in communication with the discharge end and the chamber to form a closed circuit therebetween, of means for returning a constant quantity of the sands discharged over said end to the grinding unit; and means for bypassing a portion of the sands discharged by the classifier over said discharge end to reclassify them without passagethrough the grinding unit.

6. A classifier provided with a discharge end for sands, and a settling chamber having an overflow for slimes or fine particles; a receptacle for receiving sands discharged from the said end, the receptacle being provided with an outlet; means for controlling the quantity of sands discharged through the outlet of the receptacle; and means for returning any excess material from the receptacle to the chamber,

7. A classifier provided with a discharge end for sands, and a settling chamber having an overflow for slimes or fine particles; a receptacle for receiving sands discharged from the said end, the receptacle being provided with an open bottom; a conveyor located beneath the receptacle to form a bottom therefor; and means for returning any excess material from the top of the receptacle to the chamber.

8. A classifier provided with a discharge end for sands, and a settling chamber having an overflow for slime or fine particles; a receptacle for receiving sands discharged from the said end, the receptacle being provided with an open bottom; a, conveyor located beneath the receptacle to form a bottom therefor; an adjustable gate carried by an end of the receptacle to control the depth of material on the conveyor; and means for returning any excess material from the top of the receptacle to the chamber.

9. A classifier provided with a discharge end for sands, and a settling chamber; a receptacle for receiving sands discharged from the said end, the receptacle being provided with an outlet; means for controlling the quantity of sands discharged through the outlet of the receptacle; and means including a screw conveyor for returning any excess material from the receptacle to the chamber.

10. A classifier provided with a discharge for sands and a settling chamber; a receptacle for receiving sands from the said discharge and provided with an open bottom; a conveyor located beneath the receptacle; means including a screw conveyor mounted in the receptacle to return the excess material from the latter to the chamber; and means for varying the speeds of the conveyors relative to one another.

11. A classifier provided with a settling chamber and an incline; a conveyor for conveying material from the chamber up the incline; a receptacle for receiving the material discharged from the incline; means for removing a predetermined quantity of material constantly from the receptacle; and means for returning any surplus material in the receptacle to the chamber.

12. A classifier provided with a settling chamber and an incline; a conveyor for conveying material from the chamber up the incline; a receptacle for receiving the material discharged from the incline; means for removing a lesser quantity of ma. terial constantly from the receptacle during a predetermined period of time than that discharged into the receptacle during the same time period; and means for returning any excess material from the receptacle to the chamber.

13. A classifier provided with a settling cham- -ber and a, discharge end; means for discharging material from the bottom of the chamber over the said end; a receptacle for receiving material discharged over said end; a grinding unit having an inlet; means for directing material from the receptacle to the inlet; means for controlling the quantity of material conveyed by the conveying means to the inlet of the grinding unit; and means for returning any excess material from the receptacle to the chamber.

14. A receptacle for receiving ore pulp; means for withdrawing pulp from the bottom of the receptacle; means for agitating the pulp with water intermediate the top and bottom of the pulp to separate the slimes therefrom, the receptacle having an open bottom and the first means including a conveyor located beneath the receptacle to form a bottom therefor; and means for carrying the said slimes and any excess pulp away from the top of the receptacle; and means for varying the rates of speed of the conveyor relative to the said carrying means.

15. In combination a classifier and a grinding mill in closed circuit, the'classifier including a settling chamber and a discharge end; means for drawing off settled sands from the settling chamber and discharging them over said end;'a receptacle for receiving said discharged sands; means for returning a predetermined quantity of the said discharged sands from the bottom of the receptacle to the grinding mill; means for agitating the sands with water intermediate the top and bottom of the receptacle to separate the slimes therefrom by flotation; and means for returning the said slimes and any surplus discharged sands directly to the said chamber.

16. In combination a classifier and a grinding mill in closed circuit, the classifier including a settling chamber and a discharge end for sands; means for drawing oii settled sands from the settling chamber and discharging them over the said end; means for returning a quantity of the said discharged sands to the grinding mill so that they will be re-ground before re-entry to the classifier; means for returning any surplus discharged sands directly to the settling chamber of the classifier so that such surplus sands will be reclassified before being re-ground; and means for varying the rate of speed of the said second atnlxli third mentioned means relative to one an- 0 er. 

